Detectors including scintillating means for beam index cathode ray tubes

ABSTRACT

Beam-index cathode ray tubes are depicted in combination with elongated strip-like and coiled light pipe-scintillators. Penetrating radiation which impinges upon the side walls of the elongated light pipe-scintillator creates scintillations in the interior region thereof. These scintillations are in the optical frequency range and are accumulated in strength as they travel through the light pipe. They emerge at exit terminals in concentrated form. The concentrated optical scintillations are used for beam indexing purposes in cathode ray tubes including those with multicolor producing target screens. Single, dual, and triple index signal configurations are described.

United States Patent Goodman 1 Nov. 25, 1975 [5 DETECTORS INCLUDINGSCINTILLATING 2,915,659 12/1959 Goodman 313/65 LF MEANS FOR BEAM INDEXCATHODE RAY 3,027,219 3/1962 Bradley t l l l 346/110 TUBES 3,032,6595/1962 Bacon et al 250/7115 3,081,414 3/1963 Goodman l l t l l t t.315/10 [76] Inventor: David M. Goodman, 14272 Half 3,567,935 3/1971 dman.7 250/22 X Moon Bay Drive, Del Mar, Calif. 92014 PrimaryExaminer-Robert Segal [22] Filed: Aug. 8, 1973 ABSTRACT [21] Appl 3865Beam-index cathode ray tubes are depicted in combi- Related U.S.Application Data Continuation of Ser. No. 119,504, March 1, 1973,abandoned, Division of Ser. No. 562,031, June 2, 1966, Pat. No3,567,985, which is a continuation of Ser. No. 212,612, July 26, 1962.

U.S. Cl. 313/471; 313/65 LF Int. Cl H01] 31/20; HOlj 29/08 Field ofSearch 313/471 References Cited UNITED STATES PATENTS 7/1959 Goodman313/65 LF PLASTlC 28 GLASS 24 INGI INDEX SCINTILLATOR 26 nation withelongated strip-like and coiled light pipescintillators. Penetratingradiation which impinges upon the side walls of the elongated lightpipescintillator creates scintillations in the interior region thereof.These scintillations are in the optical frequency range and areaccumulated in strength as they travel through the light pipe. Theyemerge at exit terminals in concentrated form. The concentrated opticalscintillations are used for beam indexing purposes in cathode ray tubesincluding those with multicolor producing target screens. Single, dual,and triple index signal configurations are described.

16 Claims, 14 Drawing Figures US. Patent Nov. 25, 1975 Sheet 1 of23,922,581

FIG.I .0 FIG.2 o PIC-3.3

IO l4 l4 PRIOR ART PLASTIC 28 SINGL INDEX SCINTILLATOR 26 -23 METAL'grsl PLASTIC INVENTOR ATTORNEY DETECTORS INCLUDING SCINTILLATING MEANSFOR BEAM INDEX CATI'IODE RAY TUBES CROSS-REFERENCE TO RELATEDAPPLICATIONS This application is a continuation of pending applicationSer. No. 119,504 filed Mar. 1, 1973 now abandoned.

This application is a division of my co-pending application Ser. No.562,031 filed June 2, 1966 (now scheduled to issue as U.S. Pat. No.3,567,985 on Mar. 2, I971 which in turn is a continuation on myapplication Ser. No. 212,612 filed July 26, 1962.

In my U.S. Pat. No. 3,081,414 granted 12 Mar. 1963, I describe a cathoderay tube which does not require a heated cathode. Instead, use is madeof X-rays which are emitted when the target screen of that tube isstruck by high energy electrons. These X-rays are detected byscintillators to produce light signals which are transmitted throughlight pipes to where they impinge upon photon-sensitive surfaces whichin turn emit electrons. These electrons then are multiplied, controlled,and focussed to provide a beam of cathode rays. This beam is scannedacross the target screen which causes additional X-rays to be generated,thereby to sustain the operation of the circuit. In such an arrangementthe cathode ray beam will increase in magnitude until a saturation levelis reached. The resultant energization at a given point of the targetscreen is proportional to this saturation level and is proportional tothe duration of excitation. It is possible then to modulate the outputof this heaterless tube by varying the saturation level or the durationof excitation. Thus, this arrangement provides a cathode ray tube with aclosed loop feedback system which is capable of generating a beam ofelectrons without requiring the conventional heater-cathode combination.

It becomes desirable in an arrangement such as just described toincrease the efficiency of detection of the X-rays. And this is oneobject of this invention.

Another object of this invention is to provide X-ray detection means ofimproved sensitivity that may be employed with all types of cathode raytubes, heaterless or not, having X-ray beam indexing structures.

Still another object of this invention is to provide detection means,responsive to a penetrating radiation, which may be used to increase thesensitivity of beamindex circuitry employed with multi-color cathode raytubes.

Various other objects and advantages will appear from the followingdescription taken in conjunction with the drawing. The novel featuresthereof will be particularly pointed out hereinafter in connection withthe appended claims. In the drawing:

FIG. 1 represents a cathode ray tube with a scintillator attached toelements of the electron gun of the tube.

FIG. 2 represents a cathode ray tube with a scintillator having a largearea of pick-up.

FIG. 3 represents a cathode ray tube with externally disposed X-raydetectors.

FIGS. 1, 2 and 3 represent prior art; they do not form a part of thisinvention. They are included in the drawing to better illustrate theimprovement gained by the instant invention. These three figures areincluded in the aforesaid U.S. Pat. No. 3,081,414.

FIG. 4 represents a cathode ray tube with a scintillator which isstrip-like in form. The scintillator shown is positioned adjacent to theoutside surface of the tube envelope.

FIG. 5 represents a cathode ray tube with three separate scintillatorswhich are shown adjacent the inside surface of the tube envelope.

FIG. 6 is a cross-sectional view of the tube in FIG. 5.

FIG. 7 represents a heaterless cathode ray tube where a singlescintillator is wrapped around the envelope of the tube.

FIG. 8 represents a heaterless cathode ray tube where two scintillatorsare provided similar to the construction of FIG. 7 but which are placedadjacent the inside surface of the tube envelope.

FIG. 9 represents a target screen with three different color producingregions. Associated therewith are three different index signals, one foreach color producing region.

FIG. 10a illustrates two different levels of excitation of the red stripof the target screen of FIG. 9.

FIG. 10!: illustrates two different periods of excitations of the redstrip of the target screen of FIG. 9.

FIG. 11 represents a composite target screen that may be used with acathode ray tube to provide index signals.

FIG. 11a represents an end view of the target screen of FIG. 11.

FIG. 12 represents various terminations of and a transition for thestrip-like scintillators.

Referring now to the drawing in detail, FIGS. 1, 2 and 3, whichrepresent the prior art as previously noted, are similar in that acathode ray tube has an envelope 10 containing an electron gun 12 whichis used to provide an electron beam. Element 14 is common to the threefigures in that it picks up electromagnetic radiation generated at thetarget screen of the tube in response to excitation by the electronbeam. In FIG. 1, element 14 is advantageously positioned in that it islocated with respect to the target screen so that it picks upsubstantially equal amounts of radiation from all parts of the screen.In FIG. 2 element 14 advantageously is provided with a large surface forpick-up of the radiation and has a channel provided in its body so thatthe electron beam may pass from the gun 12 to the target screen. In FIG.3, elements 14 are positioned outside of the tube and near the plane ofthe front face of the cathode ray tube.

FIGS. 1-4 represent cathode ray tubes that may be used for colortelevision receivers.

In FIG. 4, the cathode ray tube has an envelope 20 and a target screen22 positioned on, or near, the from inside surface of the envelope 20.Electromagnetic radiation is shown emanating from the target screen viapaths 36, 34, 32, and 30. In one embodiment of this invention, thetarget screen 22 is constructed so that this radiation is in the X-rayregion of the spectrum. A scintillator 26 associated with rod 24 will beexcited by those X-rays which travel along path 36 thereby producingflashes of light. These flashes will be conveyed through rod 24 by aseries of internal reflections to an exit termination thereof. It can beseen from the drawing that the area of pick-up of the X-rays is governedby a frontal area of scintillator 26 associated with rod 24. To increasethe area of pick-up, and hence the sensitivity of X-ray detection. thereis provided in accordance with this invention an elongated scintillatingmember 28 positioned on the outside of the envelope 20. For

this mode of operation it is to be understood that a horosilicate glassis to be used for the tube envelope, and that high anode voltages arecontemplated. Alternatively. ceramic materials such as BeO may be usedfor the funnel section of the CRT envelope. With this arrangement,X-rays emitted by the screen 22 will strike scintillator 28 along itslength. Paths 34, 32, and 30 are shown in FIG. 4 to illustrate thispoint and to provide a visual comparison with the effect produced by theX- rays travelling along path 36. in effect, the sensitivity of pick-upnow is governed by the length of the member 28, (and by the volume)providing a very distinct advantage.

The rod 24 preferably is made of glass since it is placed in the highvacuum region of the cathode ray tube; furthermore the glass rod itselfmay be the scintillator as can be seen by referring to US Pat. No.3,032,659 issued to J.F. Bacon, et al., on May l. 1962. On the otherhand, the strip-like member 28 may be made of a plastic scintillatorsince it is placed on the outside of the tube. Plastic scintillators arecommercially available which are easy to machine or form; which aresensitive to X-rays; which will respond rapidly to X-ray excitation; andwhich will provide light flashes which will decay very rapidly aftercessation of excitation. One example of such a plastic scintillator isthat made by Nuclear Enterprises, Limited, in Winnipeg, Canada under theidentification NE-l02. See also Hyman US. Pat No. 2,710,284. For eithertype of scintillator, the X-rays generated at the target screen 22 willproduce the desired result in that they penetrate into the interior ofthe scintillator where they produce light, and then by the process ofinternal reflection much ofthe light thus generated is transmittedthrough the scintillator to an exit termination.

it should be noted that if the radiation to be detected is in theoptical frequency range such as in the ultraviolet region then the samegeneral conditions prevail. For example, if a conventional P-16 (orcalcium magnesium silicatezcerium activated) phosphor is used forindexing it will generate ultra-violet radiation (centered at approx.3800 Angstroms) when excited by electrons. This 3800A will betransmitted through most CRT glasses (the coating of carbon or aluminumbeing removed) and will also create scintillations in the plasticphosphor strip 28. But, if the radiation is not to be detected, but isto be collected and transmitted without change in wavelength, then theadvantage gained by penetration and scintillation is no longeravailable. it is a property of light pipes, or optical fibres, that whenradiation of the type it can transmit enters the pipe from a side wallthe refraction is such that the radiation emerges from the pipe at theother side. In order for this radiation to be piped it must enter thepipe through entrance terminals, the design requirements for which arewell known. The result of such design applied to this case is that thestrip 28 can be notched, or serrated, along its length to permit theradiation to enter.

In FIG. 5, a cathode ray tube is illustrated with three strip-likescintillators 42, 44, and 46 which are symmetrically positioned insidethe envelope of the tube. Although not limited thereto, this arrangementis particularly useful for multi-color cathode ray tubes of thebeam-index variety. The three scintillators may respond to the sameexcitation to increase the sensitivity of pick-up by a factor of three.Alternatively, each scintillator may be used to pickup" a differentradiation, in which case strips 52, S4, and 56 are used to provide 4suitable filtering. When the three strips are positioned outside thetube the transmissive qualities of the envelope 40 may also be used toprovide filtering. Further elaboration is not considered necessary atthis time since the art of filtering X-rays and other radiations is welldeveloped. It is of interest, however. to notice from FIG. 4 that aburst of radiation from screen 22 traverses different paths in strikingthe scintillation member 28; and after scintillation, the light pulsestravel through different lengths in the light pipe. The result is thatthe pulse oflight created in scintillator 28 will exist for a greaterperiod of time than that of the exciting radiation. in other words, aninstantaneous emission of X-rays at screen 22 results in a pulse oflight emerging from the exit end of member 28 which exits for a finitetime. It also means that the emergent pulse of light is delayed in time.This broadening and delay of the pulse is a function of the length ofthe member 28, and of the material of which it is constructed. To delaythe output pulse of light further, as may be desired in certainapplications, alight pipe member 42' may be provided as illustrated inFIG. 5. This additional delay is useful in synchronizing the operationof color cathode ray tubes where radiation from the target is used toprovide high speed index signals, High speed, minimum delay circuitsgenerally are required with beam-index tubes intended to provide highresolution multi-color displays.

As an example, consider the index signal being used to providesynchronization of a three color display using presently known verticalstrip target screens. For a 20 inch target screen having 250 sets ofcolor triplets there are 750 strips approximately 25 mils in width. Thehorizontal scanning time, less flyback, is 5 3.5usecs. Then for a linearscanning beam, with a spot size much less than 25 mils, the time spenton each strip is approximately 0.07psecs, or nanoseconds. For a 5 milbeam and a 1 mil index wire an X-ray pulse is fur nished ofapproximately 17 nanoseconds, a fairly crisp index signal. Plasticscintillator 28 will broaden this index signal; by decay time and bytravel time. Typically, the decay time is 4 nanoseconds and is selfexplanatory, The travel time effect is explained by assuming pathlengths 30 and 34 are equal. The radiation via path 34 excites thescintillator, whereupon the light pulse travels to the exit terminationnear the neck section of the tube. The radiation via path 30 alsoexcites the scintillator, and at the same time, but the light pulse inthis case has to travel an additional distance, 33, in the scintillatorwhich takes approximately 2 nanosec onds for a 1 foot length. Thus, theresultant index signal will be lengthened from l7 to 23 nanoseconds,which is still a crisp index pulse. To delay this pulse, member 42' canprovide in a 5 foot length approximately 10 nanoseconds of delay whichis sufficient to affect vernier control of the overall delay in theindex loop. As a matter of comparison, an equal length of co-axial cablewith a 500 characteristic impedance, which is frequently used forelectrical delay lines, has a delay of approximately 8 nanoseconds.Therefore, the elongated scintillators can greatly increase thesensitivity of detection of the index signal, does so with a tolerablebroadening of the signal, and furnishes an optical" signal which may beadjustably delayed in transit.

There is shown in FIG. 6 a sectional view of the tube of FIG. 5 to showthe scintillators more clearly. The scintillators 42, 44, and 46 areshown with filters 52, 54, and 56. These elements are ribbon-like inshape and, as stated, positioned inside the tube. As an alternative toelements 42, 44, and 46 plastic scintillator 49 is positioned on theoutside of the tube with a filter element 47; and plastic scintillator51 is shown with a metal jacket 53 for filtering purposes.

With proper design it will be found that the envelope 40 attenuates onlyslightly the x-rays which are to be detected by these externallypositioned scintillators. In contrast thereto, most glasses absorbultra-violet of wavelength less than 3500A and if such signals are to bedetected (or if low energy X-rays are to be detected) then the internaldisposition of the strips is preferred. As a practical matter, thechoice of tube envelope and the placement of the detector can best bemade after the requirements for the CRT are defined. This is so becausethere are dozens of detectors and a multitude of indexing phosphors thatare available; and an almost endless variation in the compositions ofglass and ceramics that can be used for CRT envelopes.

In FIG. 7, a heaterless cathode ray tube is illustrated with ascintillating light pipe element 110 wrapped around the envelope of theevacuated tube. This is done to increase still further the quantity ofX-rays which are picked up, as should now be clear. The tube operates asfollows: at region 100 a particle is ionized, as by some natural cause.The negative ion thus formed, perhaps an electron, is accelerated by ahigh positive voltage to strike the target screen at point 102. X-raysare produced upon impact and radiate in all directions, typical pathsbeing shown at 104, 106, and 108. Many of these X-rays will createscintillations in member 110 which results in light flashes travellingin both directions as illustrated at 107. The light pipe properties ofthe scintillator enables these flashes to be transmitted via routes 112and 114 to eventually impinge upon a suitable photo-sensitive surface116. Electrons are emitted from 116 and are amplified by secondaryemission at dynodes I18 and 120 (voltage connections to the dynodes andto the target screen are not shown) and are forcussed at element 124,which thus provides a stream of electrons which are to be scanned bymeans symbolized by element 126. Element 124 may be a secondary emissiondynode equivalent to elements 118 and 120. Element 124 may be atransmission type secondary emission dynode. In effect, the latterstages of the secondary emission amplifier and the element 124 comprisean electron lens so that the beam of electrons normally provided by theheated cathode in a conventional electron gun is in this case providedby the element 124. Additional details of construction on theelectron-gun-optics are considered conventional, and therefore areomitted. Emanating therefrom is the stream of electrons 128 which isaccelerated to strike the target screen at 130. Upon impact, additionalX-rays are generated. This process is repeated until a steady statecondition is reached; then there is a constant beam current provided at128. The explanation of the manner in which this electron beam may bemodulated will be deferred until the explanation of FIGs. 9, a, and 10b,but at this point it is clear that the requirement for the conventionalcathode heater has been dispensed with.

In FIG. 8, another embodiment of a heaterless cathode ray tube is shown.This tube generates two index signals and may be used in a dual indexcolor receiver. This tube provides, in effect, two electron beams whichcan be modulated. Two spiral shaped scintillators 142 and 144 areintertwined, and positioned adjacent the funnel section of the tube. Bymeans of the scintillation process, these detectors provide two *opticalsignals, one travelling through light pipe 146 and the other through148, to impinge upon two photon-sensitive surfaces 150 and 152.Electrons generated thereby are controlled by grids 154 and 156, and aresubsequently amplified and partially focussed by dynodes 158 and 160.Then they are further focussed, as at transmission dynode 162, toprovide an electron beam 164. Deflection coil 140 provides the scanningaction of beam 164. The deflection fields created by coil 140 areseparated or shielded from the dynode; 158 and 160 and the focussingmeans 162 so as not to interact. The drawing is exaggerated to moreeasily identify the various elements and is not to scale. The shielding,and other design features, of secondary emission multipliers are wellknown and not described further since they do not assist in theunderstanding of this invention. It should be noted, however, that thehigh sensitivity of the scintilla tors provides strong light signalswhich soon run the secondary emission amplifier section into saturation.Also to be noted is that in this mode of operation if crisp indexsignals are not required the coils 142 and 144 can be of some length.The operation of this tube is similar to the tube of FIG. 7 except thattwo different radiations are produced at the target screen. Morespecifically, there is a first region of the target screen whichproduces X-rays in a given portion of the spectrum to excite thescintillator 142, and there is a second region which produces X-rays ina different portion of the spectrum to excite the scintillator 144. Thebeam current that strikes the target screen in the first region producesX-rays, which excites scintillator 142, which causes ejection ofelectrons from surface 150, etc. The beam current that strikes thetarget screen in the second region produces different X-rays whichexcite scintillator 144, which causes ejection of electrons from surface152, etc. Then, as the beam is deflected from region to region of thetarget screen the source of the electron beam switches back and forthbetween the channels represented by dynodes 154 and 156 thus making itpossible to modulate separately the beam currents. This constructionwould be used to advantage in self-decoding color television receivers.Since the circuits, per se, form no part of this invention, they are notincluded.

Referring now to FIG. 9 to discuss methods of modulation of the beam ofthe heaterless CRT there is shown a target screen comprised of phosphorstrips capable of emitting red, green, and blue light in response toelectron excitation. X-ray producing particles may be admixed with thephosphors or deposited in layers on either side thereof. Alternatively,the chemical elements of the phosphors themselves may be used togenerate the X-rays. As an illustration, the red phosphor of F G. 9 withits associated X-ray producing particles, will be considered toconstitute the entire target screen of FIG. 7. In this case the electronbeam 128 will build up to produce a constant intensity red spot on theface of the tube. This is best explained by referring to FIGS. 9 and 10gtaken together. Before proceeding with the description, it is to benoted that each strip of a different color requires its own distinctchannel for scintillation detection and for controlled amplification ofthe electron stream. Thus, a two color tube requires a dual indexsystem, as in FIG. 8. A three color system operating in this moderequires a triple index configuration. As long as the scanning fielddeflects the electron beam to region 171 to the left of the red strip ofFIG. 9 there will be a very small beam current for there are not suitable X-rays generated in this area to sustain the operation of thecircuit. Once the electron beam enters the red strip. however. there areX-rays generated, there is color (red) produced, and as illustrated inFIG. "la the beam current builds up. Curves 170 and 172 depict twodifferent levels which the beam can reach. These levels can be governedby controlling the space charges between the dynodes. Typically, a cloudof electrons are allowed to build up in one of the dynode spaces. Thenthe cloud is released by grid control as is done in other types ofelectron discharge devices. Alternatively, gain control can be employedin accordance with the teachings of US. Pat. No. 3,036,234 issued toG.C. Dacey on May 22, 1962 to set the saturation level. This patenteedescribes how semi-conductor detectors may be used in place of thesecondary emission dynodes to achieve the same end result, namely aphoton generated electron beamv Referring now to FIG. b, there is showncurve I74 which represents a saturated beam current which is gated onfor a given period of time. A second curve I76 is shown which representsthe same saturated level of beam current but which has a duration largerthan that of curve I74. As with the control of the saturation level ofFIG. 10a, so the time duration of FIG. 10!) can be controlled byapplying suitable potentials (time varying) to the dynodes 118 and 120of FIG. 7. For conventional electron guns the results illustrated inFIG. 10a and 10b can be achieved by the use of an aperture and adeflection field in the vicinity of element 124 of FIG. 7; and iffurther particulars are desired I refer to US Pat. No. 3,038,101 issuedto K. Schlesinger on June 5, 1962.

In FIG. 11 a composite target screen is shown which may be used inconjunction with a receiver system employing two different indexsignals. FIG. 11a is an end view of the composite target screen.Phosphor strips I80, 182, I84, are arranged to be scanned by an electronbeam. Aluminum layer 185 is applied over the phosphor strips. Strips I86and 188 are deposited on the aluminum layer to produce two differentindex signals. For example, when the electron beam strikes 186, X-raysare produced which are at a given wavelength. And when the beam strikes188, X-rays are produced which are distinguishable from those producedat 186. Strip 186 may be made of copper particles; strip 188 may be madeof nickel. With this construction, the aluminum layer 185 not onlyprovides the conventional function of increasing brightness but it alsomay serve as a barrier preventing chemical reactions between the indexgenerating strips 186 and I88 and the light producing strips 180, 182,and 184. A second aluminum layer, 190, is deposited over the indexstrips to prevent the appearance of an ion spot". Since it need notcover the entire screen this layer is shown terminating in the region192. In certain modes of deflection, and with certain electron guns,this layer may be omitted. However, when used this layer absorbs thenegative ions that are attracted to the target screen. It is chosen ofsufficient depth to be opaque to the ions but transparent to theelectrons and to the X-rays. This construction reduces the maskingeffect on the index signals that might otherwise be created by theimpact of the negative ions on the X-ray emitting strips 186 and 188.Alternative construction is indicated by X-ray emitting strips 194 andI98 which are jacketed or surrounded by layers I96 and 199.

ln FIGv I2 members 200, 204, and 206 represent terminations that may beused with the scintillating strips. Member 200 has a terminal with layer202 deposited thereupon. This layer, if made of aluminum for exampie, isimpinged upon by the light pulses travelling through the scintillator,and is reflected to augment the light emerging from the other end of thescintillator. This layer, if made of an opaque material such as carbon.will absorb the light pulses travelling away from the exit end. Thislatter arrangement may be desirable when the broadening ofthe lightpulses at the output is to be kept at a minumum. Member 204 has anoutwardly flared end which may be used at either end of a light pipe,serving to aid the exit of the transmitted light. It may be used. withthe coil of FIG. 7 where both ends of the coil are used as exitterminations. The end of member 206 is pinched and may be used toreflect the light from that end. Member 208 is a transition which willconvey the light from a circular light pipe to a strip-like light pipe,and vice-versa. Clearly, these terminations may be used with the stripsof FIGS. 4, 5, 6, and 8 to obtain the properties desired.

It is believed that the foregoing part of the specification has shownhow the primary objects of this invention have been achieved. X-rays. orother penetrating radiations such as ultra-violet radiation, generatedby a scanning beam of electrons in a cathode ray tube are detected byproviding adjacent to and coextensive with the envelope of said tube aspecial material which is penetrated by the radiation, whichscintillates internally, and which transmits the light generated byscintillation through the material by the process of internalreflection. It has been shown how this feature substantially increasesthe amount of radiation detected in comparison to an end-on positioningof the detector as disclosed in the prior art. It has shown that thisarrangement will provide a greatly enhanced index signal which is sharpand crisp and which can be used for synchronizing the generation of amulti-color display. It has also been shown how such a detector can beused in conjunction with light sensitive means, and the secondaryemission process, to provide the electron beam of a cathode ray tube,either monochrome or multi-color.

Having thus described my invention, I claim:

1. In a beam-index color television display apparatus comprising incombination:

1. a cathode ray tube with an envelope containing an image-producingtarget screen and an electron gun for providing a scannable electronbeam;

2. said target screen comprising a repeating array of different colorproducing strips in register with beam-index strips for generatingelectromagnetic index radiation indicative of the position of impact ofthe electron beam on the target screen;

3. means for scanning said electron beam across target screen; therebyto impact said color producing strips and said beam-index strips;

4. detection means responsive to the index radiation thus emitted fromsaid beam-index strips; and

5. means responsive to the output of said detection means for modulatingthe electron beam thereby to properly excite said color producingstrips;

the improvement in said detection means comprising an elongatedstrip-like scintillator having the properties of a light pipe and beingdisposed so as to be excited along its length via the index radiationfrom many of the beam-index strips whereby optical signals gener- 9 atedin its interior region are transmitted via a series of internalreflections to emerge at an exit terminal thereofwhere the opticalsignals are used to control the modulation of the electron beam.

2. The combination of claim 1 wherein said beamindex strips emit indexradiation in the ultraviolet region of the spectrum, and wherein saidscintillator is penetrated by and is responsive to the ultraviolet indexradiation.

3. The combination of claim I wherein the envelope of the cathode raytube comprises a faceplate section, a funnel section, and a neck sectionjoined seriatim; and wherein the elongated strip-like scintillator ispositioned proximate the funnel section.

4. The combination of claim 3 wherein said elongated scintillator isring-like in form and positioned near said faceplate.

5. The combination of claim 3 wherein said elongated scintillator isring-like in form and positioned near said neck section.

6. The combination of claim 1 wherein said elongated scintillator is inthe form of a spiral.

7. The combination of claim 1 wherein said elongated scintillator is inthe form of a coil.

8. The combination of claim 1 wherein said beamindex strips arecomprised of a first series of strips which emit electromagneticradiation in one region of the spectrum and a second series of stripswhich emit electromagnetic radiation in a different region of thespectrum, including a first striplike scintillator responsive to theradiation from said first series of strips and a second strip-likescintillator responsive to the radiation from said second series ofstrips.

9. The combination in claim 8 wherein said first series of strips emitx-radiation and said first scintillator is responsive thereto.

10. The combination of claim 8 wherein said second series of strips emitultraviolet radiation and said second scintillator is responsivethereto.

11. A beam-index line-screen multi-color cathode ray tube with anenvelope having a neck section including an electron gun for providing ascannable electron beam, a faceplate section having associated therewithan electron-sensitive target screen for generating a visible multi-colorimage in response to the scanning action of the electron beam, and afrusto-conical-like intermediate section which connects the neck sectionwith the faceplate section; said target screen comprising a repeatingarray of different color producing strips in register with a pluralityof spaced apart beam-index strips for generating electromagneticradiation index signals indicative of the position of impact of theelectron beam on the target screen; in combination with beam-indexdetection means comprising a strip-like light pipe-scintillator whichgenerates signals in the optical frequency range. in its interiorregion, in response to penetration by the index signals; said lightpipe-scintilator having a relatively broad surface disposed adjacent toand coextensive with part of said frusto-conicallike intermediatesection of the tube envelope in a radiation receiving relationship withrespect to said index signals; said light pipe-scintillator also havingat least one relatively narrow surface where said signals in the opticalfrequency range are concentrated via light pipe action.

12. A beam-index line-screen multi-color cathode ray tube with anenvelope containing a faceplate, an image-producing target screen on theinterior side of the faceplate, and an electron gun for providing ascannable electron beam; said target screen comprising a repeating arrayof different color producing strips in register with a plurality ofspaced apart electron-sensitive beam-index strips for generating primaryindex signals, in the optical frequency range, indicative of theposition of impact of the electron beam on the target screen; incombination with beam-index detection means responsive to said primaryindex signals for controlling said electron Beam; the improvement insaid detection means comprising a scintillator member disposed in alight receiving relationship with respect to said primary index signals,and characterized in that it yields a secondary optical index signal inresponse to excitation by the primary optical index signals.

13. The combination of claim 12 wherein said scintillator is in the formofa light pipe capable of being penetrated by said primary index signalsin the optical frequency range, thereby to generate in its interiorregion said secondary optical index signal.

14. The combination of claim 13 wherein said scintillator is in the formofa ribbon-like light pipe with a relatively broad surface disposed toreceive the index signals and having an exit terminal of relativelysmall dimensions; and means for receiving and utilizing the secondaryoptical index signal transmitted, via a series of internal reflections,through the light pipe scintillator to said exit terminal.

15. The combination of claim 12 wherein said spaced apart beam-indexstrips generate primary index signals in the ultraviolet region of thespectrum. and wherein the scintillator member is responsive thereto.

16. The combination of claim 12 wherein said envelope has a neck sectioncontaining the electron gun, and a frusto-conical intermediate sectionjoining said neck section to said faceplate section; and wherein saidscintillator member is disposed adjacent to and coextensive with atleast part of said intermediate section.

1. In a beam-index color television display apparatus comprising incombination:
 1. a cathode ray tube with an envelope containing animageproducing target screen and an electron gun for providing ascannable electron beam;
 2. said target screen comprising a repeatingarray of different color producing strips in register with beam-indexstrips for generating electromagnetic index radiation indicative of theposition of impact of the electron beam on the target screen;
 3. meansfor scanning said electron beam across target screen; thereby to impactsaid color producing strips and said beamindex strips;
 4. detectionmeans responsive to the index radiation thus emitted from saidbeam-index strips; and
 5. means responsive to the output of saiddetection means for modulating the electron beam thereby to properlyexcite said color producing strips; the improvement in said detectionmeans comprising an elongated strip-like scintillator having theproperties of a light pipe and being disposed so as to be excited alongits length via the index radiation from many of the beam-index stripswhereby optical signals generated in its interior region are transmittedvia a series of internal reflections to emerge at an exit terminalthereof where the optical signals are used to control the modulation ofthe electron beam.
 2. said target screen comprising a repeating array ofdifferent color producing strips in register with beam-index strips forgenerating electromagnetic index radiation indicative of the position ofimpact of the electron beam on the target screen;
 2. The combination ofclaim 1 wherein said beam-index strips emit index radiation in theultraviolet region of the spectrum, and wherein said scintillator ispenetrated by and is responsive to the ultraviolet index radiation. 3.The combination of claim 1 wherein the envelope of the cathode ray tubecomprises a faceplate section, a funnel section, and a neck sectionjoined seriatim; and wherein the elongated strip-like scintillator ispositioned proximate the funnel section.
 3. means for scanning saidelectron beam across target screen; thereby to impact said colorproducing strips and said beam-index strips;
 4. detection meansresponsive to the index radiation thus emitted from said beam-indexstrips; and
 4. The combination of claim 3 wherein said elongatedscintillator is ring-like in form and positioned near said faceplate. 5.means responsive to the output of said detection means for modulatingthe electron beam thereby to properly excite said color producingstrips; the improvement in said detection means comprising an elongatedstrip-like scintillator having the properties of a light pipe and beingdisposed so as to be excited along its length via the index radiationfrom many of the beam-index strips whereby optical signals generated inits interior region are transmitted via a series of internal reflectionsto emerge at an exit terminal thereof where the optical signals are usedto control the modulation of the electron beam.
 5. The combination ofclaim 3 wherein said elongated scintillator is ring-like in form andpositioned near said neck section.
 6. The combination of claim 1 whereinsaid elongated scintillator is in the form of a spiral.
 7. Thecombination of claim 1 wherein said elongated scintillator is in theform of a coil.
 8. The combination of claim 1 wherein said beam-indexstrips are comprised of a first series of strips which emitelectromagnetic radiation in one region of the spectrum and a secondseries of strips which emit electromagnetic radiation in a differentregion of the spectrum, including a first strip-like scintillatorresponsive to the radiation from said first series of strips and asecond strip-like scintillator responsive to the radiation from saidsecond series of strips.
 9. The combination in claim 8 wherein saidfirst series of strips emit x-radiation and said first scintillator isresponsive thereto.
 10. The combination of claim 8 wherein said secondseries of strips emit ultraviolet radiation and said second scintillatoris responsive thereto.
 11. A beam-index line-screen multi-color cathoderay tube with an envelope having a neck section including an electrongun for providing a scannable electron beam, a faceplate section havingassociated therewith an electron-sensitive target screen for generatinga visible multi-color image in response to the scanning action of theelectron beam, and a frusto-conical-like intermediate section whichconnects the neck section with the faceplate section; said target screencomprising a repeating array of different color producing strips inregister with a plurality of spaced apart beam-index strips forgenerating electromagnetic radiation index signals indicative of theposition of impact of the electron beam on the target screen; incombination with beam-index detection means comprising a strip-likelight pipe-scintillator which generates signals in the optical frequencyrange, in its interior region, in response to penetration by the indexsignals; said light pipe-scintilator having a relatively broad surfacedisposed adjacent to and coextensive with part of saidfrusto-conical-like intermediate section of the tube envelope in aradiation receiving relationship with respect to said index signals;said light pipe-scintillator also having at least one relatively narrowsurface where said signals in the optical frequency range areconcentrated via light pipe action.
 12. A beam-index line-screenmulti-color cathode ray tube with an envelope containing a faceplate, animage-producing target screen on the interior side of the faceplate, andan electron gun for providing a scannable electron beam; said targetscreen comprising a repeating array of different color producing stripsin register with a plurality of spaced apart electron-sensitivebeam-index strips for generating primary index signals, in the opticalfrequency range, indicative of the position of impact of the electronbeam on the target screen; in combination with beam-index detectionmeans responsive to said primary index signals for controlling saidelectron Beam; the improvement in said detection means comprising ascintillator member disposed in a light receiving relationship withrespect to said primary index signals, and characterized in that ityields a secondary optical index signal in response to excitation by theprimary optical index signals.
 13. The combination of claim 12 whereinsaid scintillator is in the form of a light pipe capable of beingpenetrated by said primary index signals in the optical frequency range,thereby to generate in its interior region said secondary optical indexsignal.
 14. The combination of claim 13 wherein said scintillator is inthe form of a ribbon-like light pipe with a relatively broad surfacedisposed to receive the index signals and having an exit terminal ofrelatively small dimensions; and means for receiving and utilizing thesecondary optical index signal transmitted, via a series of internalreflections, through the light pipe scintillator to said exit terminal.15. The combination of claim 12 wherein said spaced apart beam-indexstrips generate primary index signals in the ultraviolet region of thespectrum, and wherein the scintillator member is responsive thereto. 16.The combination of claim 12 wherein said envelope has a neck sectioncontaining the electron gun, and a frusto-conical intermediate sectionjoining said neck section to said faceplate section; and wherein saidscintillator member is disposed adjacent to and coextensive with atleast part of said intermediate section.